1. Field of the Invention
This invention relates to a holder for a magnetic transfer apparatus for magnetically transferring information carried by a master information carrier to a slave medium, and more particularly to a holder which accommodates therein the master information carrier and the slave medium and holds them in close contact with each other.
2. Description of the Related Art
There has been known a magnetic transfer in which a patterned master information carrier provided with an irregularity pattern or an embedded pattern representing the signals (e.g., servo signals) to be transferred and with a magnetic layer formed on at least the top surface of the irregularity pattern or the embedded pattern is brought into close contact with a slave medium, and a transfer magnetic field is applied to the slave medium and the patterned master information carrier, thereby transferring the signals to the slave medium, as disclosed, for instance, in Japanese Unexamined Patent Publication Nos. 63(1988)-183623 and 2001-256644, and U.S. Pat. No. 6,347,016.
In the case where the slave medium is a disc such as a hard disc or a high-density flexible disc, a disc-like master information carrier is brought into close contact with one side or each side of the slave medium and the transfer magnetic field is applied to the slave medium/master information carrier assembly (comprising the slave medium and the master information carrier held in close contact with each other) by an electromagnet unit or a permanent magnet unit disposed on one side or each side of the assembly.
In order to obtain a high transfer quality, it is important that the slave medium and the master information carrier are held in close contact with each other over the entire areas thereof with no dust or dirt intervening therebetween. That is, when dust or dirt intervenes between the slave medium and the master information carrier, the slave medium cannot be in close contact with the master information carrier at the portion about the dust or dirt and the magnetic transfer does not occur there, which results in dropout of signals in the transferred magnetic information. When the transferred magnetic information comprises servo signals, dropout of signals deteriorates the tracking function and lowers the reliability.
Since the information carried by a master information carrier is transferred to a number of slave media by repeated use of the master information carrier, when dust or dirt adheres to the surface of the master information carrier, defective transfer occurs in all the subsequent magnetic transfers, and at the worst, the dust or dirt can deform the surface of the master information carrier and damages the regular function of the master information carrier.
In the magnetic transfer, the master information carrier and the slave medium are generally accommodated and held in close contact with each other in a holder comprising a chamber base and a chamber body which are moved toward and away from each other. In order to purge air from between the slave medium and the master information carrier to bring them into closer contact or to bring them into close contact with each other, the inner space of the holder is sometimes sealed and evacuated.
The chamber base and the chamber body are moved toward and away from each other to put the slave media in and out from the inner space of the holder and the pressing faces of the chamber base and the chamber body are moved toward and away from each other to press the slave medium and the master information carrier against each other to bring them in close contact with each other. The inner space of the holder formed between the chamber base and the chamber body should be sealed and the pressing faces of the chamber base and the chamber body must be moved toward and away from each other keeping the inner space sealed each time the magnetic transfer is effected. Conventionally, the inner space of the holder is sealed and is kept sealed during movement of the pressing faces of the chamber base and the chamber body by the same sealing member. However when the inner space of the holder is sealed and is kept sealed during movement of the pressing faces of the chamber base and the chamber body by the same sealing member, the service life of the sealing member is shortened to make it necessary frequent change of the sealing member, which results in deterioration of the working efficiency, and dust or dirt becomes apt to be generated due to wear of the sealing member, which results in defective transfer as described above.